Remove tools/services.md and add stackblitz.md

.gitignore

@@ -9,3 +9,6 @@ build
 # Dev directories
 /app/bower_components
 /node_modules
+/scripts/node_modules
+/scripts/temp
+/scripts/*_analysis.json

app/2.0/docs/devguide/custom-elements.md

@@ -52,6 +52,8 @@ Polymer adds a set of features to the basic custom element:
 *   Creating shadow DOM trees for element instances based on a supplied template.
 *   A data system that supports data binding, property change observers, and computed properties.
 
+
+
 ## Custom element lifecycle {#element-lifecycle}
 
 The custom element spec provides a set of callbacks called "custom element reactions" that allow you
@@ -218,33 +220,8 @@ by any pending lifecycle callbacks.
 
 Element upgrades allow you to place elements in the DOM while deferring the cost of initializing them. It's a progressive enhancement feature.
 
-Elements have a *custom element state* that takes one of the following values:
-
-
-
-*   "uncustomized". The element does not have a valid custom element name. It is either a built-in
-    element (`<p>`, `<input>`) or an unknown element that cannot become a custom element
-    (`<nonsense>`)
-*   "undefined". The element has a valid custom element name (such as "my-element"), but has not
-    been defined.
-*   "custom". The element has a valid custom element name and has been defined and upgraded.
-*   "failed". An attempt to upgrade the element failed (for example, because the class was invalid).
-
-The custom element state isn't exposed as a property, but you can style elements depending on
-whether they're defined or undefined.
-
-Elements in the "custom" and "uncustomized" state are considered "defined". In CSS you can use the
-`:defined` pseudo-class selector to target elements that are defined. You can use this to provide
-placeholder styles for elements before they're upgraded:
-
-```
-my-element:not(:defined) {
-  background-color: blue;
-}
-```
-
-**`:defined` is not supported by the Custom Elements polyfill.** See the [documentation on styling](style-shadow-dom#style-undefined-elements) for a workaround.
-{.alert .alert-warning}
+To avoid showing unstyled content, you can add styles for elements that haven't upgraded yet. For 
+details, see [Style undefined elements](style-shadow-dom#style-undefined-elements).
 
 ## Extending other elements {#extending-elements}
 

app/2.0/docs/devguide/registering-elements.md

@@ -133,7 +133,7 @@ customElements.define('x-class', XClass);
 ```
 
 The `mixinBehavior` function also mixes in the Legacy APIs, the same as if you extended
-`Polymer.LegacyElement`. These APIs are required since since hybrid behaviors depend on them.
+`Polymer.LegacyElement`. These APIs are required since hybrid behaviors depend on them.
 
 ## Define an element in the main HTML document {#main-document-definitions}
 

app/2.0/docs/devguide/style-shadow-dom.md

@@ -512,6 +512,8 @@ class myElement extends Polymer.Element(){
 }
 ```
 
+[See an example on Plunker](http://plnkr.co/edit/vWS9PIBTTbKHxRnJyT7T?p=preview)
+
 ### Style directional text with the :dir() selector
 
 The `:dir()` CSS selector allows for styling text specific to its orientation